Embodiments of the present invention relate to acidic milk and soy beverages having improved stability. In particular, embodiments of the present invention relate to weakly acidic flavored milk and soy beverages comprising a carrageenan stabilizer system.
The beverage industry has considerable interest in providing healthy, on-the-go beverages that have a desirable flavor, texture, and appearance. One example of such a beverage includes acidic fruit juice-containing milks; however, numerous challenges are associated with creating stable acidified milk-juice drinks. For example, there may be significant difficulties in providing stable protein complexes over the shelf-life of the product and ensuring proper suspension of the protein complexes and insoluble ingredients such as minerals, pulp, and fiber.
Protein protection at low pH is critical to prevent aggregation of the milk proteins during acidification and thermal processing of the beverage. The proteins found in neutral pH milk are relatively small in micellular size and possess a net negative charge that allows the particles to repel one another and remain in solution. As the pH of the milk approaches the isoelectric point of the protein, around pH 4.6, the net charge on the protein is reduced and the proteins have a tendency to self-associate, or aggregate. As the pH is further reduced below the isoelectric point, this effect worsens and additional heat treatment of the beverage exacerbates instability such that the denatured proteins strongly aggregate, causing dense sedimentation to occur over the shelf-life of the beverage. This can result in an appearance that consumers often find unappealing at best, and proteins that have an unpleasant mouthfeel and that are extremely difficult to re-disperse at worst.
Maintaining small protein particle sizes (i.e., micellular sizes) is necessary to maintain the stability of these beverages, as is demonstrated by Stokes' Law. Conventional stabilizers such as pectin, cellulose gum, soy bean fiber, and propylene glycol alginate are employed to minimize the association of these proteins during beverage processing. These anionic polymers act as protective hydrocolloids by associating with the protein below its isoelectric point, and inhibiting the extensive protein-protein interactions that would otherwise result from their reduced charge repulsion. Proper colloidal protection allows the protein micellular size to remain small (around 1.0 μm) and stable over the shelf life of the drink.
The afore-mentioned protective colloids are most effective within a pH range of 3.5 to 4.2. Although beverages produced at these pH typically have a pleasing flavor profile with considerable acid bite, it is desirable to provide stable acidified milk-juice beverages with higher pH such that milder fruit flavors can be formulated with a less-tart taste. These products have pH values of around 5.0 to 5.5, which are above the desirable operating range for the most commonly used protective hydrocolloids.
In general, milk-based beverages produced between a pH of 5.0 and 5.5 are above the isoelectric point of the protein, making electrostatic interactions between an anionic hydrocolloid and a weakly-negatively charged protein extremely difficult to achieve. As such, other, preferably natural, stabilizers are desirable in order to stabilize the protein in this weakly acidic pH range, while accommodating existing ultra high temperature (UHT) sterilization, high temperature/short time (HTST) pasteurization, and other processes used to heat-treat milk beverages.